The volcano in America that gives scientists the biggest headache

The snow-covered peak of Mount Rainier, 4,300 m high in Washington state, USA, has had no major eruptions in the past 1,000 years. However, surpassing the boiling lava fields in Hawaii or the Yellowstone super volcano, Rainier worries American volcanologists the most.

“Rainier keeps me up at night because it poses such a huge threat to the surrounding community. Tacoma and South Seattle are built on 100 feet of ancient mudflow from Mount Rainier’s eruptions,” said volcanologist Jess Phoenix.

The danger of this sleeping giant is not the hot lava, which, if it erupts, would not flow more than a few kilometers beyond the boundaries of Mount Rainier National Park. Much of the volcanic ash would also be carried eastward by winds, away from population centers, according to the U.S. Geological Survey (USGS).

Instead, many scientists worry about the prospect of lahars — fast-moving streams of water and volcanic rock that originate from melting snow and ice from volcanic eruptions, carrying debris as they flow through valleys and drainage channels.

“What makes Rainier so dangerous is that it is very high and covered with snow and ice. So if any eruption occurs, the hot material will melt the cold material and a huge amount of water will begin to form.” “There are tens, even hundreds of thousands of people living in areas that could potentially be affected by a major lahar, and it could happen quite quickly,” said Seth Moran, a seismologist at Taiwan. USGS Cascades Volcano Observatory, said.

The deadliest recent lahar occurred in November 1985, when the Nevado del Ruiz volcano in Colombia erupted. Just hours after the eruption began, a river of mud, rocks, lava and water swept through the town of Armero, killing more than 23,000 people in just a few minutes.

Rainier had about eight times more snow and ice than Nevado del Ruiz did then, according to Bradley Pitcher, a lecturer in Earth and environmental sciences at Columbia University. “A much more catastrophic mud flood is at risk of happening,” he said.

A 2022 study simulated two worst-case scenarios. In the first simulation, a lahar flow with a volume of 260 million cubic meters and a thickness of 4 meters begins to flow down from the western slope of Mount Rainier. According to Moran, this mudflow would be equivalent to 104,000 Olympic-sized swimming pools and could reach the densely populated lowlands of Orting, Washington state, about an hour after the eruption. The mud stream will move at a speed of about 4 m per second. According to the second simulation, the Nisqually River valley will suffer when a giant lahar flow could carry water from Alder Lake, overflowing the 100 m high Alder Dam.

The USGS established a lahar detection system at Mount Rainier in 1998, then upgraded and expanded it in 2017. About 20 locations on the volcano’s slopes and two roads were identified as having a high risk of lahars. Most are now equipped with broadband seismometers, which transmit real-time data, and many other devices such as trap lines, infrasound sensors, cameras and GPS receivers.

In March of this year, about 45,000 students from the Puyallup, Sumner-Bonney Lake, Orting, White River and Carbonado areas of Washington state participated in a lahar evacuation drill. According to the USGS, it was the first time that so many schools from different areas participated in the same drill, making it the largest lahar drill in the world.